[moderation] [net?] KCSAN: data-race in page_pool_put_unrefed_netmem / page_pool_refill_alloc_cache

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3609fa95fb0f Merge tag 'devicetree-fixes-for-6.19-2' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=145a2f92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=8e2fce773b4d87da4c56
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [da...@davemloft.net edum...@google.com ha...@kernel.org ho...@kernel.org ilias.ap...@linaro.org ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3018b7ea95aa/disk-3609fa95.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b7f25f6e87af/vmlinux-3609fa95.xz
kernel image: https://storage.googleapis.com/syzbot-assets/13d7f9c6c13e/bzImage-3609fa95.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8e2fce...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in page_pool_put_unrefed_netmem / page_pool_refill_alloc_cache

write to 0xffff8881504cb100 of 8 bytes by task 15800 on cpu 0:
__ptr_ring_zero_tail include/linux/ptr_ring.h:259 [inline]
__ptr_ring_discard_one include/linux/ptr_ring.h:291 [inline]
__ptr_ring_consume include/linux/ptr_ring.h:311 [inline]
page_pool_refill_alloc_cache+0x2a5/0x3c0 net/core/page_pool.c:402
__page_pool_get_cached net/core/page_pool.c:441 [inline]
page_pool_alloc_netmems net/core/page_pool.c:659 [inline]
page_pool_alloc_pages+0xd0/0x130 net/core/page_pool.c:675
page_pool_dev_alloc_pages include/net/page_pool/helpers.h:96 [inline]
xdp_test_run_batch net/bpf/test_run.c:295 [inline]
bpf_test_run_xdp_live+0x54d/0x11d0 net/bpf/test_run.c:379
bpf_prog_test_run_xdp+0x525/0x970 net/bpf/test_run.c:1388
bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4703
__sys_bpf+0x4c0/0x7c0 kernel/bpf/syscall.c:6182
__do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
__x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6272
x64_sys_call+0x28e1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:322
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881504cb100 of 8 bytes by task 15801 on cpu 1:
__ptr_ring_produce include/linux/ptr_ring.h:106 [inline]
page_pool_recycle_in_ring net/core/page_pool.c:786 [inline]
page_pool_put_unrefed_netmem+0x38b/0x4b0 net/core/page_pool.c:907
page_pool_put_netmem include/net/page_pool/helpers.h:343 [inline]
page_pool_put_full_netmem include/net/page_pool/helpers.h:373 [inline]
napi_pp_put_page+0xe9/0x200 net/core/skbuff.c:1018
skb_pp_recycle net/core/skbuff.c:1029 [inline]
skb_free_head+0x12c/0x150 net/core/skbuff.c:1076
skb_release_data+0x33b/0x370 net/core/skbuff.c:1107
skb_release_all net/core/skbuff.c:1182 [inline]
__kfree_skb+0x44/0x150 net/core/skbuff.c:1196
sk_skb_reason_drop+0xbd/0x270 net/core/skbuff.c:1234
kfree_skb_reason include/linux/skbuff.h:1322 [inline]
udp_recvmsg+0x11a/0xb90 net/ipv4/udp.c:2154
inet_recvmsg+0x143/0x290 net/ipv4/af_inet.c:891
sock_recvmsg_nosec net/socket.c:1078 [inline]
sock_recvmsg+0xf6/0x170 net/socket.c:1100
____sys_recvmsg+0xf5/0x280 net/socket.c:2812
___sys_recvmsg+0x11f/0x370 net/socket.c:2854
do_recvmmsg+0x1ef/0x540 net/socket.c:2949
__sys_recvmmsg net/socket.c:3023 [inline]
__do_sys_recvmmsg net/socket.c:3046 [inline]
__se_sys_recvmmsg net/socket.c:3039 [inline]
__x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3039
x64_sys_call+0x2b75/0x3000 arch/x86/include/generated/asm/syscalls_64.h:300
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffea0005e45800 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 15801 Comm: syz.2.4531 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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